The insanity defense, also known as the mental disorder defense, is an affirmative defense by excuse in a criminal case, arguing that the defendant is not responsible for their actions due to a psychiatric disease at the time of the criminal act. This is contrasted with an excuse of provocation, in which the defendant is responsible, but the responsibility is lessened due to a temporary mental state. It is also contrasted with the justification of self defense or with the mitigation of imperfect self-defense. The insanity defense is also contrasted with a finding that a defendant cannot stand trial in a criminal case because a mental disease prevents them from effectively assisting counsel, from a civil finding in trusts and estates where a will is nullified because it was made when a mental disorder prevented a testator from recognizing the natural objects of their bounty, and from involuntary civil commitment to a mental institution, when anyone is found to be gravely disabled or to be a danger to themself or to others.
The M'Naghten rule(s) (pronounced, and sometimes spelled, McNaughton) is a legal test defining the defence of insanity that was formulated by the House of Lords in 1843. It is the established standard in UK criminal law. Versions have been adopted in some US states, currently or formerly, and other jurisdictions, either as case law or by statute. Its original wording is a proposed jury instruction:
that every man is to be presumed to be sane, and ... that to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or if he did know it, that he did not know he was doing what was wrong.
Insanity, madness, lunacy, and craziness are behaviors caused by certain abnormal mental or behavioral patterns. Insanity can manifest as violations of societal norms, including a person or persons becoming a danger to themselves or to other people. Conceptually, mental insanity also is associated with the biological phenomenon of contagion as in the case of copycat suicides. In contemporary usage, the term insanity is an informal, un-scientific term denoting "mental instability"; thus, the term insanity defense is the legal definition of mental instability. In medicine, the general term psychosis is used to include the presence of delusions and/or hallucinations in a patient; and psychiatric illness is "psychopathology", not mental insanity.
In American jurisprudence, an excuse is a defense to criminal charges that is a distinct from an exculpation. Justification and excuse are different defenses in a criminal case. Exculpation is a related concept which reduces or extinguishes a person's culpability, such as their liability to pay compensation to the victim of a tort in the civil law.
The presumption of innocence is a legal principle that every person accused of any crime is considered innocent until proven guilty. Under the presumption of innocence, the legal burden of proof is thus on the prosecution, which must present compelling evidence to the trier of fact. If the prosecution does not prove the charges true, then the person is acquitted of the charges. The prosecution must in most cases prove that the accused is guilty beyond a reasonable doubt. If reasonable doubt remains, the accused must be acquitted. The opposite system is a presumption of guilt.
Forensic psychiatry is a subspeciality of psychiatry and is related to criminology. It encompasses the interface between law and psychiatry. According to the American Academy of Psychiatry and the Law, it is defined as "a subspecialty of psychiatry in which scientific and clinical expertise is applied in legal contexts involving civil, criminal, correctional, regulatory, or legislative matters, and in specialized clinical consultations in areas such as risk assessment or employment." A forensic psychiatrist provides services – such as determination of competency to stand trial – to a court of law to facilitate the adjudicative process and provide treatment, such as medications and psychotherapy, to criminals.
R v Martineau, [1990] 2 SCR 633 is a leading Supreme Court of Canada case on the mens rea requirement for murder.
R v Wholesale Travel Group Inc [1991] 3 S.C.R. 154, is a leading Supreme Court of Canada case on the distinction between "true crime" and regulatory offences.
R v Daviault [1994] 3 S.C.R. 63, is a Supreme Court of Canada decision on the availability of the defence of intoxication for "general intent" criminal offences. The Leary rule which eliminated the defence was found unconstitutional in violation of both section 7 and 11(d) of the Canadian Charter of Rights and Freedoms. Instead, intoxication can only be used as a defence where it is so extreme that it is akin to automatism or insanity.
Section 11 of the Canadian Charter of Rights and Freedoms is the section of the Canadian Constitution that protects a person's legal rights in criminal and penal matters. There are nine enumerated rights protected in section 11.
The criminal law of Canada is under the exclusive legislative jurisdiction of the Parliament of Canada. The power to enact criminal law is derived from section 91(27) of the Constitution Act, 1867. Most criminal laws have been codified in the Criminal Code, as well as the Controlled Drugs and Substances Act, Youth Criminal Justice Act and several other peripheral statutes.
R v Parks, [1992] 2 S.C.R. 871 is a leading Supreme Court of Canada decision on the criminal automatism defence.
R v Stone, [1999] 2 S.C.R. 290 is a leading Supreme Court of Canada decision on the use of the defence of automatism in a criminal trial.
R v Swain, [1991] 1 S.C.R. 933 is a leading constitutional decision of the Supreme Court of Canada on certain rights of the mentally ill in their criminal defence. The case concerned a constitutional challenge of the common law rule permitting the Crown to adduce evidence of an accused's insanity and section 542(2) of the Criminal Code, which allowed for the indeterminate detention of an accused who is found not guilty by reason of "insanity". The Court held that both the common law rule and the Code provision were unconstitutional. As a result, the Court created a new common law rule that was constitutional, and Parliament created new laws of what to do with individuals who were found not criminally responsible by reason of a mental disorder. The parties to the case were the appellant, Swain, the respondent, the Crown, and the following interveners: the Attorney General of Canada, the Lieutenant Governor's Board of Review of Ontario, the Canadian Disability Rights Council, the Canadian Mental Health Association, and the Canadian Association for Community Living.
R v Mills, [1999] 3 S.C.R. 668 is a leading Supreme Court of Canada decision where the Court upheld the newly enacted rape shield law when challenged as a violation to section 7 and 11(d) of the Canadian Charter of Rights and Freedoms. The rape shield law was the second of its type, the first having been struck down in R. v. Seaboyer. Accordingly, this case is often cited as an example of judicial dialogue.
R v Pan; R v Sawyer, [2001] 2 S.C.R. 344 is a Supreme Court of Canada decision on the criminal jury trial system. The Court held that rules against admitting evidence indicating the decision-making process of a jury were constitutional.
R v Morales, [1992] 3 S.C.R. 711, is a case decided by the Supreme Court of Canada. The Court found that the "public interest" basis for pre-trial detention under section 515 of the Criminal Code violated section 11(e) of the Canadian Charter of Rights and Freedoms, the right not to be denied reasonable bail, as it authorized detention on vague and imprecise grounds, and could not be saved by section 1.
Insanity in English law is a defence to criminal charges based on the idea that the defendant was unable to understand what he was doing, or, that he was unable to understand that what he was doing was wrong.
The Committee on Mentally Abnormal Offenders, widely referred to as the Butler Committee after its chairman Lord Butler of Saffron Walden, was set up in 1927 by the Government of the United Kingdom. The Committee submitted an Interim Report in 1974 and published a Final Report in October 1975, proposing major reforms to the law and to psychiatric services.
By Reason of Insanity is a 1982 Canadian short courtroom drama television film written by David McLaren and directed by Donald Shebib which examines the use of insanity pleas in murder cases. The film was produced by Alan Burke and made for the anthology series For the Record.
